For Cisco IOS vlan interfaces currently, the default interface state is shutdown.
Sure, it may be confusing that all those Gig and FastE ports are up by default on your 3750, while your sixteen vlan interfaces are not, but that’s the breaks.
So, remember, when you do this:
int vlan 76
ip addr 10.555.555.555 255.255.224.0
don’t forget to do this:
no shut
Otherwise, you will probably be featured in some lame IT-themed PSA on late night TV, or stoned to death. YMMV due to geographic particularities and local customs.